[x/tour] go-tour: fix format function
[x/tour] go-tour: fix format function

Once Go 1.1 is out we can use go/format.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/8698048
X-Tour-Commit: eb434147af906053f7ec0d041687ca422e850109

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website